Utility

Solution preparation

Calculates how much concentrated stock and how much sterile water (or other diluent) to combine to produce a target volume of a target concentration. Useful for making D5W from 50% dextrose, half-strength saline, and similar bench preparations.

Worked example

To make 1 L of D5W from a 50% dextrose stock: draw 100 mL of 50% dextrose and combine with 900 mL of sterile water for injection. Math: (1000 mL × 5%) ÷ 50% = 100 mL stock; remaining 900 mL is diluent.

Target volume (mL)

Final volume you want to end up with.

Target concentration (%)

Common: 5 (D5W), 2.5 (half-strength D5W), 0.45 (half-strength saline).

Stock concentration (%)

Pick the concentrate you have on hand. Most clinics carry 50% dextrose.

Recipe

100mL stock

of 50% solution

Combine with

900 mL of sterile water for injection (or 0.9% NaCl if appropriate)

Total: 1000 mL of 5% solution (50 mg/mL)

Target volume: 1000 mL
Target concentration: 5%
Stock concentration: 50%

Common preparations

D5W (5% dextrose) from 50% stock: 1 part stock + 9 parts sterile water (e.g., 100 mL + 900 mL = 1 L).
D2.5W from 50% stock: 1 part stock + 19 parts sterile water (e.g., 50 mL + 950 mL = 1 L).
Half-strength saline (0.45%) from 0.9%: 1 part stock + 1 part sterile water (1:1).

Notes

Use sterile water for injection (or 0.9% NaCl as the diluent if appropriate for the application).
Prepare fresh and label clearly with concentration, date/time, and preparer initials.
Hypertonic dextrose solutions (>5%) should be administered through a central line to avoid phlebitis.
This tool does the C₁V₁ = C₂V₂ math; clinical judgment about which solution is appropriate for the patient stays with the practitioner.